1. Field of the Invention
The present invention relates generally to implantable cardiac leads, and more particularly to an active fixation lead system having a small diameter lead body and an introducer for improved maneuverability during implantation.
2. Background Art
An implantable intravascular lead assembly is oftentimes implanted for cardiac pacing, and comprises an electrical conductor which is adapted to be suitably connected to a source of electrical energy. The electrical conductor, in turn, includes an electrode tip which engages the endocardial tissue for stimulation and sensing. The lead assembly is intravenously inserted through a body vessel, such as a vein, into one or more cardiac chambers. The conductor is sealed from body fluids by a bio-compatible and bio-stable insulating material. A sheath is provided for improving the maneuverability of the conductor when inserted into, and guided through the veins for positioning in the heart chamber.
In a typical lead assembly, the electrode tip is firmly lodged in, and permanently secured to the endothelial lining of the heart. This lead assembly is referred to as an endocardial lead. Some examples of conventional endocardial leads may be found in the following publications: U.S. Pat. No. 3,348,548 to Chardack; U.S. Pat. No. 3,754,555 to Schmitt; U.S. Pat. No. 3,814,104 to Irnich et al.; U.S. Pat. No. 3,844,292 to Bolduc; and U.S. Pat. No. 3,974,834 to Kane. The teachings of these patents relate to various endocardial leads which are purportedly simple to manufacture and relatively easy to use by the operating physician.
The most desirable attributes of an endocardial lead are: (1) lead diameter and secure fixation of the electrode to the cardiac tissue to prevent electrode tip dislodgement; (2) implantation control with minimal damage to the vein, heart valve, cardiac tissue or other tissue that comes in contact with the lead, and for providing protection from over-perforation of the electrode through the cardiac tissue; and (3) removability.